other than one being alternating current and the other being direct current just what is the difference? i have done alot of stick welding, tig welding, and mig welding but to my knowledge its all been AC. reason i ask is i have a ancient welder that been in the weeds for several years that was in a barn before it fell. I believe its a lincoln sae 400 and probably dc. thats the closest thing i could find on the web that looks close. this one is 3 phase and i am considering a repower with a tractor engine i already have.